Photoflash lamp

ABSTRACT

A percussive-type photoflash lamp in which the inner wall of the lamp envelope is provided with an indicator spot containing a fluorescent dye sensitive to the combustion products of the fulminating material of the primer in order to permit automated inspection and rejection of those lamps or subassemblies thereof during manufacture in which the fulminating material has been flashed inadvertently. Refractive pigments substantially transparent to ultraviolet light are included to obtain easier visual inspection in ordinary light and a substantial increase in emitted light intensity under ultraviolet light.

United States Patent Inventors Thomas B. McDonough Allenwood;

John W. Shaffer, Williamsport, both of, Pa. Appl. No. 878,163 Filed Nov. 19. 1969 June 22, 1971 Sylvania Electric Products inc.

Patented Assignee PHOTOFLASH LAMP 4 Claims, 1 Drawing Fig.

U.S. Cl 431/13, 252/408, 431/93 int. (31 F2lk 5/02 Field of Search 431/93, 95, 94, 13

[56] References Cited UNITED STATES PATENTS 2,726,527 12/1955 Pipkin .1 431/95 3,195,326 7/1965 Shaffer 431/13 Primary Examiner- Edward J. Michael Attorneys-Norman J OMalley and Joseph C. Ryan ABSTRACT: A percussive-type photoflash lamp in which the inner wall of the lamp envelope is provided with an indicator spot containing a fluorescent dye sensitive to the combustion products of the fulminating material of the primer in order to permit automated inspection and rejection of those lamps or subassemblies thereof during manufacture in which'the fulminating material has been flashed inadvertently. Refractive pigments substantially transparent to ultraviolet light are included to obtain easier visual inspection in ordinary light and a substantial increase in emitted light intensity under ultraviolet light.

PATENTFH JUHZQIQFI THOMAS B. MCDONOUGH JOHN W. SHAFFER INVENTORS C gm ATTORNEY PHOTOFLASH LAMP This invention relates to the manufacture of photoflash lamps and more particularly to those of the percussive type.

Generally speaking, a percussive-type photoflash lamp comprises an hermetically sealed, light-transmitting envelope containing a source of actinic light and having a primer secured thereto. More particularly, the percussive-type photoflash lamp may comprise a length of glass tubing constricted to a tip at one end thereof and having a primer sealed therein at the other end thereof. The length of glass tubing which defines the lamp envelope contains a combustible such as shredded zirconium foil and a combustion-supporting gas such as oxygen. The primer may comprise a metal tube and a charge of fulminating material on a wire supported in said tube.

The fulminating material generally comprises a mixture of red phosphorus, potassium chlorate and a powdered metal such as zirconium. It must be extremely sensitive to impact ignition to ensure high lamp reliability of flashing with the desirably low-impact energies delivered by the firing mechanism. At the same time, the metal tube of the primer is thin walled and soft so as to minimize the required impact and afiord the maximum lamp reliability. Operation of the percussive-type photoflash lamp is initiated by an impact onto the tube to cause deflagration of the fulminating material up through the tube to ignite the combustion disposed in the lamp envelope.

Although the fulminating material must have a very high impact sensitivity in order to ensure the reliability of lamp flashing in the finished product, it presents very substantial problems and difficulties with respect to the manufacture and handling of individual lamps in a high-speed, mass production operation. Very minor bumping or jarring of the intermediate product structure of the lamp during its manufacture can cause the fulminating material to flash. If such accidental flashing of the fulminating material occurs prior to the introduction of the compressed oxygen atmosphere into the intermediate product structure, it goes unnoticed because the shredded combustible, even if present, does not burn. Such lamps with spent fulminating material are, of course, inoperative.

The foregoing problem is unique to flashlamps of the percussive type. Conventional filament-ignited flashlamps may be subjected to electrical continuity checking of the filament lead wire assembly and the beads of ignition paste are visible rather than concealed within a metal tube. On the other hand, nondestructive tests, such as visual or X-ray inspection of percussive-type photoflash lamps, fail to show whether or not the fulminating material has been discharged or flashed during lampmanufacturing operation. When destructive testing techniques, such as flashing of sample lamps, show a high incidence of lamps with preflashed material, the entire production group must be scrapped because the defective lamps cannot be segregated. Such losses make the manufacture of percussive-type photoflash lamps a formidable operation, increasing the cost of the finished product to the consumer, and could result in unintentional marketing of defective lamps. While the occurrence of such inadvertent ignitions might possibly be avoided or minimized by handling the lamps with extreme care on an individual basis, the cost of such a procedure would be prohibitive.

In view of the foregoing, one of the principal objects of this invention is to greatly facilitate the manufacture of percussivetype photoflash lamps on high-speed automated equipment and at the same time provide the necessary quality control attendant such manufacture. More specifically, one of the principal objects of this invention is to facilitate the segregation of prematurely flashed primer assemblies at various stages during lamp-manufacturing operations as well as thereafter.

One technique for segregating such lamps that proved to be of insufficient sensitivity and reliability involved an additive to the fulminating material that would impart a cloudy appearance to the lamp if inadvertent ignition occurred while the lamp contained air but which would not produce such an effect in a completed lamp filled with oxygen.

Another suggestion has been the formulation of certain organic dyestuffs which react with the minute..quantities of phosphorus pentoxide given off by the burning fulminating material to produce a color change. A spot of such a dye-containing formulation may be applied to the inner wall of the lamp envelope. This spot has a given initial color. In the event of an inadvertent firing of the fulminating material the color of the spot changes irreversibly to permanently indicate that this particular lamp is defective. Although this technique has the advantage that it affords the user an opportunity to inspect the lamp prior to using it, it is not adaptable to automated machine inspection of the lamps at various stages of their manufacture.

As pointed out in the copending application of John W. Shaffer, filedon even date herewith and assigned to the same assignee as this invention, it has been found that certain fluorescent dyes cease to fluoresce in the presence of combustion products of percussive flashlamp fulminating material. Thus, a spotting fluid may be compounded from such a fluorescent dye, a suitable binding resin, a pH buffering agent and a humectant. Such spots are applied onthe inner surface of the lamp envelope. Exposure to ultraviolet light causes the spot to fluoresce, which fluorescence may be monitored with a photocell. Flashing of the fulminating material in the percussive flashlamp assembly causes a rapid and complete loss of fluorescence in the spot. Although this indicator spot provided advantages and constituted a significant improvement over the techniques employed prior thereto, it became apparent that there was room for considerable further improvement. The intensity of the emitted light left much to be desired, particularly insofar as adaptation of the technique to automatic inspection on high-speed manufacturing equipment is concerned. In addition, the spot was a faintly colored transparent one in ordinary light, and this left much to be desired because it is usually desirable during manufacturing to be able to visually inspect for the presence and position of the spot in the lamp.

In view of the foregoing, one'of the principal objects of this invention is to provide a means of increasing the emitted light intensity of fluorescent flashed primer indicating spots. Another purpose is to provide a more intensely fluorescent spot which has equivalent response to the combustion products of the burned fulminating material. An additional purpose is to provide a fluorescent spot which is more readily detected on automated equipment. Still another purpose is to provide a spot which is readily detected visually in ordinary light.

These and other objects, advantages and features are attained, in accordance with the principles of this invention, by the inclusion of refractive pigments in the fluorescent spotting fluid. It has been found that the use of light-refracting pigments which are substantially transparent to ultraviolet light in fluorescent spots for indicating inadvertently flashed primer produces spots which permit easier visual inspection in ordinary light and which have an emitted light intensity of about one-third greater than spots without these pigments. The increased fluorescent intensity gives greater contrast against any stray light present in the photocell housing and thereby facilitates the reliable use of these pigmented fluorescent spots with automatic detector systems.

In a specific embodiment of the invention illustrated in the accompanying drawing, the single FIGURE is a sectional elevational view of a percussive-type photoflash lamp embodying the principles of this invention.

The lamp comprisesa length of glass tubing defining an hermetically sealed lamp envelope 2 constricted at one end to define an exhaust tip 4 and shaped to define a seal 6 about a primer 8 at the other end thereof. The primer 8 comprises a metal tube 10, a wire anvil l2 and a charge of fulminating material 14. A combustible such as filamentary zirconium 16 and a combustion-supporting gas such as oxygen are disposed within the lamp envelope. The wire anvil 12 is centered within the tube and held in place by a crimp 18 just above the head 20 of the anvil. Additional means, such as lobes 22 on wire anvil 12, are also used to aid in stabilizing and supporting it substantially coaxial within the primer tube 10 and insuring clearance between the fulminating material 14 and the inside wall of the tube 10. A refractory bead 24, fused to the wire anvil 12 just above the inner mouth of the primer tube 10, eliminates burn-throughs and functions as a deflector to deflect and control the ejection of hot particles of fulminating material from the primer tube.

An indicator spotting fluid in accordance with the principles of this invention may be represented by the following formulation:

1 part by weight 4,5 dichlorofluorescein,

4 parts by weight sodium bicarbonate,

130 parts by weight glycerol,

360 parts by weight of 10 percent solution of low viscosity, partially hydrolized polyvinyl alcohol in distilled water, and

180 parts by weight of 5 micron crystalline silicon dioxide, a

refractive pigment.

A spot 26 of this indicator fluid applied on the inner wall of the lamp envelope 2 has an emitted light intensity about 33 percent greater than the fluid not containing the crystalline silicon dioxide. The resultant spot is opaque in visual appearance under ordinary light, while the spot not containing the refractive pigment is transparent and nearly invisible.

It will be readily understood and appreciated by those skilled in the art that the composition of a satisfactory spotting fluid may vary substantially from the formulation of the specific embodiment just described without departing from the spirit and scope of this invention. For example, humectants, binders, buffers and acid-sensitive fluorescent dyes other than the specific ones noted above and in different ratios may be employed satisfactorily. in addition, many other materials may be used as refractive pigments substantially transparent to ultraviolet light, such as glass, titanium dioxide, calcium silicate, zinc oxide, calcium carbonate, magnesium oxide and aluminum oxide.

The indicator spot of this invention containing a refractive pigment substantially transparent to ultraviolet light makes possible the practical automatic detection of flashed fulminating material. Lamps in which the fulminating material of the primer has not been flashed will have a spot which fluoresces in ultraviolet light and the emitted light therefrom can be detected on instrumentation employing a photocell or other suitable detection equipment. Lamps in which the fulminating material of the primer has been ignited inadvertently will have a spot which has lost its fluorescent properties because of the action thereon of the combustion products of the burned fulminating material. These lamps may be detected by the absence of emitted light and a suitable mechanism used to relO ject them.

What we claim is:

l. A photoflash lamp comprising:

an hermetically sealed, light-transmitting envelope;

a quantity of filamentary combustible material located within said envelope;

a combustion-supporting gas in said envelope;

a primer secured to and extending from one end of said envelope, said primer including a charge of fulminating material;

and means located within said envelope for indicating the functional condition of said fulminating material, said means comprising a fluorescent dye sensitive to combustion products of said fulminating material and a refractive pigment substantially transparent to ultraviolet light.

2. The combination of claim 1 in which said indicating means is a spot of a fluid formulated from the combination of a binder, a solvent, a humectant, a buffer, an acid-sensitive fluorescent dye and a refractive pigment substantially transparent to ultraviolet light. I 3. The combination of claim 2 1n WhlCh the binder 1S polyvinyl alcohol, the humectant is glycerine, the buffer is sodium bicarbonate, the acid-sensitive fluorescent dye is dichlorofluorescein and the refractory pigment is silicon dioxide.

4. The combination of claim 1 in which said indicating means is a spot of a fluid having the following formulation of parts by weight:

1 part dichlorofluorescein,

4 parts sodium bicarbonate,

130 parts glycerol,

360 parts of 10 percent solution of low viscosity, partially hydrolyzed polyvinyl alcohol in distilled water, and

l parts of silicon dioxide. 

1. A photoflash lamp comprising: an hermetically sealed, light-transmitting envelope; a quantity of filamentary combustible material located within said envelope; a combustion-supporting gas in said envelope; a primer secured to and extending from one end of said envelope, said primer including a charge of fulminating material; and means located within said envelope for indicating the functional condition of said fulminating material, said means comprising a fluorescent dye sensitive to combustion products of said fulminating material and a refractive pigment substantially transparent to ultraviolet light.
 2. The combination of claim 1 in which said indicating means is a spot of a fluid formulated from the combination of a binder, a solvent, a humectant, a buffer, an acid-sensitive fluorescent dye and a refractive pigment substantially transparent to ultraviolet light.
 3. The combination of claim 2 in which the binder is polyvinyl alcohol, the humectant is glycerine, the buffer is sodium bicarbonate, the acid-sensitive fluorescent dye is dichlorofluorescein and the refractory pigment is silicon dioxide.
 4. The combination of claim 1 in which said indicating means is a spot of a fluid having the following formulation of parts by weight: 1 part dichlorofluorescein, 4 parts sodium bicarbonate, 130 parts glycerol, 360 parts of 10 percent solution of low viscosity, partially hydrolyzed polyvinyl alcohol in distilled water, and 180 parts of silicon dioxide. 